burnt rubber problem -- mercaptan or disulfide?

Ascorbic acid and copper is the standard treatment for dimercaptan. It's not as fast as copper on H2S but it does work, although it may take _months_. Also, The Wine Lab recommends treatment with Norit A (IIRC) after the ascorbic & copper has done its thing, otherwise the stink may recur.

If you've already treated the wine with copper, you may not need to add any more. Depends on how heavy the previous dose of copper was.

Fix it now, before blending. If you can't get rid of the smell don't use it at all. No sense making two bad carboys out of one.

Tom S

For what it's worth, as a brewer of beer, burnt rubber is associated with yeast autolysis. I don't know if this could collerate to wine.

Brewer Bob

Thanks Tom.

I waited until my cold was gone, at which point the burnt rubber was more noticeable as a smell and not just by taste. I finally did treat this wine with Ascorbic acid about 36 hours ago, and the undesirable odour/taste is greatly diminished already.

Richard

A brief update for the sake of anyone who may in the future follow this thread in the archives:

Nearly a month after treating with ascorbic acid, the wine smells and tastes just fine. I haven't found any need to treat with more copper

-- I'm assuming that there was still enough in solution to deal with the mercaptans once they ascorbic acid broke down the disulfides. In any case I'll leave in bulk storage for at least a few more months before declaring a victory :-)

Richard

Not too many months, Richard. Once a wine has been fixed, as you did, it's best drunk as soon as possible. I found that the problem has a propensity to come back after a while.... Cheers, Giovanni.

The Wine Lab recommends that after treatment you fine with carbon (which I think will bind with all the copper/sulfide complexes in the wine), and then filter this out, or else the problem will definitely come back. Based on my experience with 1 bad batch of Cab, they're right.

Ed

I've learned the hard way that mercaptan problems are difficult to eliminate and keep from coming back. After dealing with it a couple times to my dissapointment, I decided to focus on prevention rather than cure. For reds, proper nutrient for the yeast and plenty of aeration (I use rack and return w/aeration) during primary fermentation does the trick. For whites, propert nutrient for the yeast and selection of yeasts with very low or no H2S production.

CHEERS!!

Because wine is such a reductive environment, the tendency is always towards forming sulphides and worse.

Aaron's right you really have to stay on top of the problem, but even doing this you wil get the occasional sulphide problem.

If you do you need to recognise it quickly and treat appropriately - air for ferments, DAP or other nitrogenous nutrients if the Baume is not below 4 or

5 (after this the yeast can no longer transport nutrients across the cell wall due to inhibition by alcohol). Post ferment - rack off lees at first sign of problems, aerate reds (watch SO2), and/or treat with Copper.

If you can deal with the sulfides, you shouldn't encounter the mercaptans later.

Rob L

Hmm. That hasn't been my experience, either with 5 gal batchs at home or 1000 gal batches in the winery.

And I've never used it, so I'm no expert, but I had thought activiated carbon was sort of a last resort, that it tended to strip wines of most of their character?

No?

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com

Dave,

I'm certainly not an expert here, but here's what I was told by the Wine Lab - they said that the aggregate copper & sulfide can separate again after a few months, and the only way to avoid this is to add deodorizing carbon to bind with these and then remove them by filtration with a polish grade filter. They suggest trials with the carbon to find the minimum amount that will remove all traces of the sulfide odor and minimize the impact on other characteristics of the wine. In their sulfide treatment instructions, they state loudly: "WITHOUT CARBON, DISULFIDES USUALLY RE-EMERGE" (emphasis is theirs).

Ed

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Hmm. Thta seems wierd. I usually trust the Wine Lab, but that just doesn't even seem coherent to me, even less actually right.

If you treat the problem with copper and/or ascorbic, then it won't smell any more. But if it doesn't smell any more, what exactly do you look for with carbon trials? Diminution of something that's no longer there anyway? :-)

I normally filter or rack the wine in short order after treating it, so maybe that's why I haven't had problems: the copper-sulfide compounds can't fall apart 'cause they're no longer there.

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com

You're right - I'm not really sure how to judge the effectiveness of the carbon (obviously I got it wrong since the smell returned) - their instructions say "The wine smells clean when the right dose of carbon is reached". As a home wine maker without sophisticated lab resources, that's what I went by. But maybe you've done all that was needed by filtering.

Ed

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I thought this too - people I know that make 'blank' ferments and then flavour them afterwards use this to strip yeast/off flavours before adding essences. Also, I've known people 'rescue' the alcohol from bad batches of wine by stripping them with a/charcoal first, then similarly using the resulting liquid as a blank/base for flavouring.

Cheers!

Shaun aRe -

Thanks for all the info guys! I'll try and filter earlier vs later, and in the meantime consider the carbon option.

In my case the problem came from being careless and leaving the wine on the gross lees too long and without regular stirring. Just got too busy with other things and pushed my luck too far. Won't be letting

*that* happen again!

Cheers, Richard

That's a good lesson for all of us to learn.

Ed

Unfortunately, they're right. I've observed this effect myself.

Tom S

Hi Tom,

I wasn't disputing (or meaning to dispute) that Cu-S compounds can decompose over time. What I was disputing was the idea that because this can occur, it's a good idea to treat all wine you've treated with copper with activated charcoal. THAT, to my mind, is insane.

I also pointed out that if the copper worked, there's no way to do a bench trial to determine what amount of charcoal to add. There's no way to look for a loss of something that isn't there.

The other possibility, for wines that have been successfully treated with copper but then later (in the bottle) start to stink again, is that not all (or any, if ascorbic isn't used) of the disulfides were broken and made available to the copper. The olfactory threshold for disulfides is enough higher than that for mercaptans or H2S that you can have disulfides, not know it, use copper to treat mercaptans and H2S, and later have the disulfides (under reductive conditions) break back into mercaptans which you CAN smell.

Without having done GC/MS before treating with copper, I don't know how you'd distinguish this situation from the one described by the Wine Lab. In both cases, a wine would appear to have been successfully treated with copper, but would then start to smell of mercaptans later.

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com

Is deodorizing carbon the same as activated carbon? Ed quoted the WL as using deodorizing while Dave referred to activated :-(